Performance and energy consumption evaluation of a fertiliser drawn forward osmosis (FDFO) system for water recovery from brackish water

Agriculture consumes approximately 70% of total freshwater worldwide. With limited freshwater resources, alternative water resources are required. This study investigated the performance of a fertiliser drawn forward osmosis (FDFO) system for water recovery from synthetic brackish water with repeated use of a cellulose triacetate (CTA) FO membrane under varying fertiliser draw solution (DS) concentrations (0.5, 1 and 2 M KCl); membrane orientations (FO vs PRO) and flow rates (100, 200 and 400 mL/min); with the corresponding effects on the specific energy consumption (SEC). Results demonstrated a robust CTA membrane with no damage. An increased DS concentration from 0.5 to 1 M KCl contributed to a three-fold increase in flux, followed by a 30 to 50% increase for 2 M KCl and a reduced SEC. Membrane orientation and flow rate had insignificant effects on performance, however, flow rate contributed to an SEC increase. FO mode at a lower flow rate combined with a higher DS concentration produced the lowest possible SEC. The study illustrated a potential lower energy process for water recovery from synthetic brackish water whilst at the same time producing a diluted fertiliser that could potentially be used for fertigation.